The present invention relates generally to systems and methods for determining position and, more particularly, to a method and system for locating and tracking the global position of a remote unit worn by a user.
The Global Positioning System (GPS), a network of approximately twenty-four satellites and twelve ground stations, has long been utilized as an aid to navigation. A typical GPS receiver unit can determine its global position by receiving position and velocity data from three or more GPS satellites and including doppler shift measurements in the calculations. More recently, GPS technology has been utilized in search and rescue applications.
The problem of notifying a rescue team of the position of a distress signal was recognized in U.S. Pat. No. 5,554,993 to Brickell. The '993 patent proposes transmitting a single approximate position to a single rescue team who then attempts a rescue. Although assumably effective in operation, the broad range of agencies, emergency personnel, and persons associated with the person initiating the distress signal are not simultaneously or quickly notified. Such notification is particularly necessary and desirable in the case of a child who is lost, injured, or abducted.
Another significant problem with present GPS systems is maintaining the power supply of the remote signaling unit. Although U.S. Pat. No. 5,703,598 attempts to solve this problem by enabling the remote unit to signal its position for short periods of time, the system requires a central station to repetitively solicit the remote signal.
It is therefore desirable to have a system and method having a remote unit which upon user activation receives and transmits global position data ultimately to a computer network database server which displays the geographic position and associated personal information at a globally accessible network location. It is also desirable to have a remote unit which only receives and transmits signals at predetermined times following activation so as to conserve battery power.